In the current era women often delay attempts to conceive to their thirties and forties, ages associated with higher rates of infertility due to reproductive aging. Despite variability in the age of onset of infertility, no validated markers exist to monitor an individual woman's fertility. The objective of this project is to examine the ability of markers of ovarian aging to predict infertility due to reproductive aging, with the long term goal to develop a model that projects individual loss of reproductive potential. We hypothesize that markers of ovarian aging are associated with natural fecundability (probability of conception per menstrual cycle), predictive of infertility, and associated with the probability of live birth. The proposed study will enroll 750 women from the community, who desire to conceive, and obtain baseline measures of ovarian aging: early follicular phase serum follicle stimulating hormone (FSH) and anti-m|llerian hormone (AMH). Participants will be actively followed throughout their attempts to conceive over the following twelve months. During that time, women will conduct standardized pregnancy testing and complete a daily and monthly diary for collection of detailed exposure data. Pregnancy follow-up will include ultrasound assessment for viability and a pregnancy outcome report. These methods will allow us to address our primary research aims: 1) Establish the marker of ovarian aging that best predicts infertility. To address this aim we will determine a) measures of association between FSH (in urine and serum) and AMH and lack of conception at 6 and 12 months and b) test characteristics (e.g. sensitivity & specificity) of each marker; 2) Develop a predictive model for age-related infertility, incorporating demographics, reproductive history, and markers of ovarian aging; and 3) Generate preliminary estimates of the association between markers of ovarian aging and miscarriage. Our study is innovative in its use of a population of unproven reproductive potential with previous access to contraception and at risk for reproductive aging. Results from this research, combined with research by others, will allow women to predict their current and future reproductive potential, ultimately allowing them more reproductive control.